Since https://review.openstack.org/#/c/163462/ and https://review.openstack.org/#/c/162649/4 in gnocchi, all kind of aggregations have been moved in the same URI namespace (/v1/aggregation/...) and we can use complex query to make aggregation across multiples metrics. This change sync the ceilometerclient alarm shell to match these changes. Change-Id: I5717a4604af5505dfb8c56463e2bdb86c59e41ce